Our objective is to measure morphological, kinetic and cytochemical characteristics of several cell populations during their temporal and proliferative progression to senescence. Such data from many individual cells in each population will be analyzed to discern the role of proliferation, mutation and delayed expression in the manifestation of senescence. The patterns of senescence in diploid rodent and human cells which occur predictably after a characteristic number of cell divisions will be analyzed and compared to one another as well as to aneuploid cells whose senescence has been induced by mutagens. Special attention will be given to contrasting senescence in cells with possible DNA repair deficiency (xeroderma pigmentosum, ataxia telangiectasia and progeria) to normal cells under stress from mutagen exposure. A time-lapse, video-microscope will record sequential images of cells during their growth. Analysis by computer-optimized techniques will provide detailed statistical characterization of normal cell populations as well as those which senesce, transform, or die. A history of each cell in the population will be reconstructed and correlated both with colorimetric and cytochemical interrogation of certain molecular states of the cell and with its eventual biological fate. Morphological data which will be acquired for cells include: shape, cross-sectional area and the occurrence of pyknosis or lysis. Kinetic data which will be acquired are interdivisional time, duration of mitosis, and rate of movement. Autoradiography, cytochemistry and colorimetry at post-mortem examinations can discern loss of membrane function, reduction or loss of macromolecular synthetic activity, change in DNA or protein content and reduction in DNA repair activity. By contrasting normally responding cells to those sensitive to specific mutagens, the role of mutation in cellular senescence, transformation, and death may be inferred. The data will be analyzed in an attempt to differentiate between various theories involving molecular mechanisms which may underlie the pathological processes of aging and carcinogenesis.